Process for obtaining copper linings



- fglass a very faintly blue color if observed by f Patented use. 12, 1939 PROCESS FOR. OBTAINING COPPEBLINNGS Paolo Misciatte'lll, Rome, Italy Nof Drawing. Application June 7, loavrsenai No. 35,914. In Italy July 1, 1m

2 Claims.

The subject matter of my present invention is a process for obtaining copper linings, e. g. for I the manufacture of copper mirrors, and the D copper or silver mirrors obtained by such methods.

My present invention is based on the discovery that formaldehyde is capable of reducing, in the cold, the cuprotartaric- (or cuproglycericl complex to metallic copper in the presence of traces of precipitated silver, or traces of colloidal silver.

The'invention is now described in greater detail by means of the following exemplary embodiment thereof which, however, is solely illustrative and not limitative in character.

Example ride and distilled water. A known silvering solution is prepared, comprising for instance ammoniacal silver nitrate and invert sugar, and this solution is added: by so proceeding that the silver-is deposited in so,th'in a layer as to give the transparency. The glass plate thus prepared 'is again washed with water, and then the Solution A 25 (see below) is rapidly poured out thereon so as to suddenly flood the whole plate.

Solution A 4 g. of copper sulphate, 15 g. of Seignettesalt 'isodic potassic tartrate) and 6 g. caustic soda 1 in sticks are dissolved in 1,000 g. of distilled water,

and to this solution '15 cc. of a 1%arabic gum solution are added. Immediately before apply ing such solution 100 cc. of commercial 40% forma aldehyde is added.

According to my present invention the reaction between formaldehyde and caustic soda ispresurrounding atmosphere.

A sheet of glass is washed with stannous chlo- -a very thin layer of silver on said support, an

" arable, a cuprotartrate. and water. f

vented by the presence of traces of a colloid, such 7 reaction would produce a consequent development of hydrogen which would cause the detachment of the copper layer from its support.

When operating at ordinary tem' rature for obtaining a good andsufliciently t ck'deposit of copper, a time of from half to one hour will be needed according to the temperature of the A preferred form of realization of the invention has been above described, but it is understood by those skilled in thelart that both the solution and the processmay be modified in their non-essential details invention. 7

Having now particularly described and ascertained the nature of nrv said invention and in what manner the same is to be performed, I declare that what I claim is: 1. The process for the production of copper 80 linings for the manufacture of copper mirrors,

coppered silvered mirrors and the like, comprising precipitating metallic .copper in the cold by. reduction with a reducing agent consisting of formaldehyde in the. presence of'silverfrom 'a 35 solution consisting of caustic soda, gum arable,

a cuprotartrate, and water.

2. The process for the production of a copper lining upon a support, comprising first producing then'precipitating a lining of metallic copper in the. cold on said thin silver layer by reductionwith a reducing agent consisting of formaldehyde from a solution consisting of caustic soda, gum.

raono .as arabic gum, agar-agar, or the like, as such' within the scope of; my I 

